Spot welding of a secondary part to a closed section part, preferably formed by hydroforming can be accomplished by a spot welding assembly as disclosed in United States Patent Publication no. 2004/0065641. In this apparatus, the electrodes are positioned on opposite sides of the closed section part, sandwiching the secondary part therebetween. Application of electrical current welds the two components together.
This apparatus works well in applications where the secondary part wraps about the closed section part so that the two electrodes can contact from opposite sides of the closed part. However, in other applications where the secondary part does not wrap, it is very difficult to insert the electrode in the closed section and position the tip in more remote regions inside of the closed section.